mirror of
https://github.com/jart/cosmopolitan.git
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130 lines
4.5 KiB
C
130 lines
4.5 KiB
C
/*-*- mode:c;indent-tabs-mode:t;c-basic-offset:8;tab-width:8;coding:utf-8 -*-│
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│vi: set et ft=c ts=8 tw=8 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ $OpenBSD: ecvt.c,v 1.11 2019/01/25 00:19:25 millert Exp $ │
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│ │
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│ Copyright (c) 2002, 2006, 2010 Todd C. Miller <millert@openbsd.org> │
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│ │
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│ Permission to use, copy, modify, and distribute this software for any │
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│ purpose with or without fee is hereby granted, provided that the above │
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│ copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES │
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│ WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF │
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│ MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR │
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│ ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES │
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│ WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN │
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│ ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF │
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│ OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. │
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│ │
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│ Sponsored in part by the Defense Advanced Research Projects │
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│ Agency (DARPA) and Air Force Research Laboratory, Air Force │
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│ Materiel Command, USAF, under agreement number F39502-99-1-0512. │
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│ SUCH DAMAGE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/fmt/fmt.h"
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#include "libc/mem/mem.h"
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#include "libc/str/str.h"
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#include "libc/str/unicode.h"
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#include "third_party/gdtoa/gdtoa.h"
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asm(".ident\t\"\\n\\n\
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OpenBSD ecvt/gcvt (MIT)\\n\
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Copyright (c) 2002, 2006, 2010 Todd C. Miller <millert@openbsd.org>\"");
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asm(".include \"libc/disclaimer.inc\"");
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// clang-format off
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#define DEFPREC 6
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char *
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gcvt(double value, int ndigit, char *buf)
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{
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char *digits, *dst, *src;
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int i, decpt, sign;
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struct lconv *lconv;
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lconv = localeconv();
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if (ndigit <= 0) {
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/* Match printf(3) behavior. */
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ndigit = ndigit ? DEFPREC : 1;
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}
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digits = dtoa(value, 2, ndigit, &decpt, &sign, NULL);
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if (digits == NULL)
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return (NULL);
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if (decpt == 9999) {
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/*
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* Infinity or NaN, convert to inf or nan with sign.
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* We can't infer buffer size based on ndigit.
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* We have to assume it is at least 5 chars.
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*/
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snprintf(buf, 5, "%s%s", sign ? "-" : "",
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*digits == 'I' ? "inf" : "nan");
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freedtoa(digits);
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return (buf);
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}
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dst = buf;
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if (sign)
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*dst++ = '-';
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/* Match printf(3) behavior for exponential vs. regular fomatting. */
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if (decpt <= -4 || decpt > ndigit) {
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/* exponential format (e.g. 1.2345e+13) */
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if (--decpt < 0) {
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sign = 1;
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decpt = -decpt;
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} else
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sign = 0;
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src = digits;
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*dst++ = *src++;
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if (*src != '\0') {
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*dst++ = *lconv->decimal_point;
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do {
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*dst++ = *src++;
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} while (*src != '\0');
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}
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*dst++ = 'e';
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if (sign)
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*dst++ = '-';
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else
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*dst++ = '+';
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if (decpt < 10) {
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*dst++ = '0';
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*dst++ = '0' + decpt;
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*dst = '\0';
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} else {
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/* XXX - optimize */
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for (sign = decpt, i = 0; (sign /= 10) != 0; i++)
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continue;
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dst[i + 1] = '\0';
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while (decpt != 0) {
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dst[i--] = '0' + decpt % 10;
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decpt /= 10;
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}
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}
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} else {
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/* standard format */
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for (i = 0, src = digits; i < decpt; i++) {
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if (*src != '\0')
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*dst++ = *src++;
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else
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*dst++ = '0';
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}
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if (*src != '\0') {
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if (src == digits)
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*dst++ = '0'; /* zero before decimal point */
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*dst++ = *lconv->decimal_point;
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while (decpt < 0) {
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*dst++ = '0';
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decpt++;
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}
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for (i = decpt; digits[i] != '\0'; i++) {
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*dst++ = digits[i];
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}
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}
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*dst = '\0';
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}
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freedtoa(digits);
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return (buf);
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}
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